Ja. Fuentealba et al., Chronic morphine treatment and withdrawal increase extracellular levels ofnorepinephrine in the rat bed nucleus of the stria terminalis, J NEUROCHEM, 75(2), 2000, pp. 741-748
Extracellular levels of norepinephrine (NE) and glutamate (Glu) in the vent
ral bed nucleus of the stria terminalis (vBNST) of saline- and chronic morp
hine-treated rats, with or without withdrawal, were studied by means of the
in vivo microdialysis technique in anesthetized rats. In addition, the tis
sue concentration of NE was studied at different rostrocaudal levels of the
vBNST. Chronic morphine treatment significantly increased extracellular le
vels of NE, but not Glu, in vBNST. At 48 h after naloxone-induced morphine
withdrawal there was a further significant increase in the extracellular le
vels of NE, but not Glu, in vBNST. The presence of UK 14304, an alpha(2)-ad
renergic agonist, induced a significant decrease in NE extracellular levels
in all experimental groups. In contrast, UK 14304 induced a significant de
crease in Glu extracellular levels only in saline-treated rats. The results
also show that the vBNST presents a rostrocaudal gradient of NE and contai
ns 9.4% of total brain NE. The increase in NE extracellular levels in vBNST
induced by chronic morphine treatment and the further increase in NE level
s 48 h after naloxone-induced morphine withdrawal suggest that NE in vBNST
may be involved in the pharmacological effects of chronic morphine and with
drawal.